The present invention generally relates to heating appliances and, in a preferred embodiment thereof, more particularly relates to fuel-fired fireplace insert apparatus adapted to receive, heat and return air to a room in which the insert apparatus is operatively disposed.
While a wood burning fireplace, during operation thereof, adds visual warmth to the room in which it is disposed it carries with it a well known set of disadvantages such as the periodic necessity of carrying wood to the fireplace from an outside storage area and appropriately stacking it in the fireplace, tending to the fire to keep it going at the desired intensity, emptying and carrying away the ashes created by the use of the fireplace, preventing sparks and embers from being thrown into the room, and periodically removing soot deposits from the interior of the chimney. Additionally, while the typical wood burning fireplace tends to aesthetically warm its room it is far less efficient in actually warming the room, with most of the available wood combustion heat simply going up the chimney.
A conventional alternative to burning real logs in a fireplace is to install a "gas log" assembly in the fireplace interior. A gas log assembly basically includes a stacked arrangement of artificial, noncombustible logs positioned over a gas burner arrangement to which a gaseous fuel, such as natural gas, is piped. When the burner is lit, flames pass upwardly through the noncombustible artificial logs to create the appearance of a natural wood fire in the fireplace. This solves many of the problems associated with natural wood fires, since the artificial logs are not consumed by the flames, do not throw off sparks and embers, do not have to be periodically poked, stoked and otherwise tended, and do not soot up the chimney interior. Additionally, the gas log fire can be instantly started, stopped and adjusted.
However, like its natural log counterpart, the typical gas log assembly is highly inefficient from the standpoint of transferring combustion heat to the room in which it is disposed. A very large percentage of the combustion heat generated by the burning of the continuously supplied gaseous fuel simply goes up the chimney and is wasted to the outside.
In an effort to alleviate this notable shortcoming of the typical gas log assembly, various types of fireplace "inserts" have previously been proposed for installation in existing masonry fireplace openings or into the corresponding fire box opening of a prefabricated factory built fireplace. The typical conventional fireplace insert apparatus is provided in its interior with an appropriate fuel-fired gas log assembly as generally described above, and is further provided with a heating passage through which room air is sequentially received, flowed through into heat exchange contact with hot combustion gases being discharged from the fireplace insert during operation thereof, and then returned to the room as heated supply air.
Thus, a substantial portion of the combustion heat that would otherwise be simply sent up the chimney or flue is efficiently transferred to the room via the heated room air discharged from the fireplace insert. This heating throughflow of room air that traverses the interior of the fireplace insert may be via a natural convection process or created by a forced air circulating fan appropriately installed in the fireplace insert.
Despite their elimination of the gas log and wood-burning fireplace problems mentioned above, conventional fuel-fired fireplace inserts of the recirculating air flow type just described have various well known problems, limitations and disadvantages of their own. These are due primarily to the fact that a conventional fuel-fired fireplace insert of this general type is typically provided with an external draft hood structure projecting upwardly from its top side, and a separate heat exchanger structure disposed on the rear side of the insert.
The placement of the combustion gas-to-recirculated room air heat exchanger structure on the rear side of the fireplace insert either limits the maximum depth of the insert fire box portion, thereby giving it an undesirably "shallower" visual appearance, or undesirably increases the maximum horizontal depth of the insert.
The draft hood portion of the conventional fuel-fired fireplace insert, which is typically external to the insert and projects upwardly beyond its top side, performs three primary functions in the overall operation of the insert. First, it provides an outlet discharge flow path for the hot combustion gases generated in the fire box portion of the insert. Second, it functions to draw in dilution air from the room, for mixture with and cooling of the flue gases being discharged. Third, it functions in a conventional manner as a pressure "buffer" between the outlet vent and the interior of the insert.
To provide adequate room dilution air to this conventionally positioned draft hood structure it is customarily necessary to leave vertical gaps between opposite sides of the installed insert and the corresponding vertical sides of the fireplace opening. This undesirably increases the minimum size of the opening that the insert will fit into. As will be appreciated, it is aesthetically necessary to cover these vertical gaps extending along the opposite sides of the installed insert. However, because of the dilution air flow quantity required to meet the applicable codes and certification standards, it is necessary to use the perforated gap-covering trim structures supplied with the insert--it is typically not feasible to provide custom trim pieces to provide the installed insert with a different appearance.
In view of the foregoing it can readily be seen that a need exists for an improved fuel-fired, heating air recirculating type fireplace insert apparatus that eliminates, or at least substantially reduces, the above-mentioned problems, limitations and disadvantages commonly associated with conventional fuel-fired, heating air recirculating fireplace inserts of the type generally described above. It is accordingly an object of the present invention to provide such improved fireplace insert apparatus.